Electrical system for photographic color separation



June 4, 1968 M. A. MICHALSKI 3,387,179

ELECTRICAL SYSTEM FOR PHOTOGRAPHIC' COLOR SEPARATION Filed Oct. 5, 1966INVENT OR WKJYM/ZM V ,4. M04441 w/ aw ATTORNEY United States PatentOffice 3,387,179 Patented June 4, 1968 3,387,179 ELECTRICAL SYSTEM FORPHOTOGRAPHIC COLOR SEPARATION Maksymilian A. Michalski, Woodside, N.Y.,assignor to Berkey Photo, Inc., New York, N.Y. Filed Oct. 5, 1966, Ser.No. 584,429 5 Claims. (Cl. 315312) The pesent invention relates to :anelectric system for making photographic direct screen color separationsfrom color transparencies.

In the commonly used methods of preparing color printing plates fourcolor separation negatives or positives must be made for each of theprinting plates. The continuous tones of the original must also beconverted to halftones which the press can print. There are the twofundamental photographic operations, color separation and screening.Doing both color separation and halftone screening in the same step iscalled direct screening" which has been done for many years. However,the long exposure times required for exposing slow films through both afilter and halftone screen and lack of an organized work procedure hasdiscouraged wide use of the system.

Another improvement in the art occurred With the development of a singlecolor correction mask for use with the transparency to make the fourseparation negatives thus replacing the multiple masks heretofore used.In producing the color correction mask a single exposure records each ofthe necessary photographic mask images in a different layer of the samepiece of film. During processing these mask images are changed to colordye images. In preparing separation negatives, the finished single colorcorrection masking film is registered with the original transparencyfrom which it was made. Separation filters are used to selectautomatically the correct mask image. This mask image, in turn, correctsthe separation negative that is being exposed. By the use of the singlemasking film the separation procedure is essentially fixed. Further, thedevelopment of eflicient enlargers with high intensity light sources andfaster film has reduced the long exposure times heretofore required.However, the steps involved must be carried out in total darkness" andthus the chances of making errors are ul licd I H The present inventionaims to overcome the difliculties by providing an electrical circuit forelectrically programming the operations required in producing colorseparation negatives from color transparencies.

I In accordance with the invention this is accomplished by providing amain exposure lamp, a flash panel, an electrical circuit, and timedswitching means for energizing the lamps in accordance with settings forexposures of predetermined lengths.

Another object of the invention is to provide an electrical system whichis simple and economical in manufacture, efiicient -in operation, anddurable in use.

Other objects and advantages of the invention will be apparent from thefollowing description and from the accompanying drawing which shows, byway of example, an embodiment of the invention.

In making separation negatives using the direct screen system theseparation procedure is standardized for all acceptable transparencies.The tone reproduction requirements in this system are not related to thedensity range of the transparencies. It has been determined that inreproducing any transparency with this system the most importantconsideration is to achieve the proper tone rendering from highlight-sthrough upper middle tones which is quite independent of the tonerendering of the total range of the transparency.

Different shop conditions and transparencies require use of a trialmethod to produce the first satisfactory control negative withacceptable highlight dot size for a particular condition. However, oncethese exposures are established they remain constant and will be equalfor all later transparencies. The first set of negatives is producedfrom a table which contains recommended exposure times for the fourdifferent color separations. The first set of negatives is examined andif necessary one or more new sets of negatives are made until asatisfactory set of control negatives is made. The exposure times andlens opening number of the satisfactory separation negatives arerecorded and used to set exposures as hereinafter described. In makingthese separation negatives, after the main exposure, each separationnegative with the exception of the black negative is given "a flashexposure with the screen in position. The length of flash exposure isdetermined initially and does not change thereafter with the nature ofthe transparency.

Thereafter, in making color separation negatives from othertransparencies, it is only necessary to measure the highlight densitywhich varies from one transparency to another, the recorded exposuretimes remaining the same provided the lens opening is adjusted dependingupon the highlight of the particular negative.

The apparatus to make the separation negatives includes a graphic artsenlarger with :a registration system for the color correction mask andtransparency. Preferably the enlarger is adjustably mounted on a columnabove a vacuum easel type on an enlarging table. Suitable screens may beplaced in registration for each color separation over the separationfilm on the easel. Mounted on the enlarging table is a flash paneladapted to be swung over the separation film for 'a flash expo-sure.Exposure control and switching means is contained in a console typeprogramming unit conveniently mounted for manipulation by the operatorwhile in position before the enlarging table.

The programming unit includes a timing unit, means for setting thetiming unit for exposures of varying lengths for both the main and flashexposures and switching means for control of room light, vacuum system,for the vacuum easel, filter wheel control means, and a light meter.

In making color separation negatives using the electric system inaccordance wit-h the invention, the color correction mask is exposed ina conventional manner in a contact printing frame or the negativecarrier of the enlarger. The developed mask is registered over thetransparency and placed in the transparency holder of the enlarger. Theimage is projected to the desired size and focused on the vacuum easelwhile the room light is switched off. A focusing switch when pressedactuates the main light source which is used for focusing and sizing ofthe projected image, the filter wheel being automatically positioned sothat there is no filter before the lens.

The timing units for each of the color separations are set for both mainand flash exposures according to the recorded values obtained in makingthe control negatives. The light meter control dials are set to thevalues obtained in making the controlnegatives.

The light meter probe is positioned in the highlight area of theprojected image on the easel, and the aperture of the lens adjusted toproduce the same reference reading on the meter as obtained with thecontrol negative. Thereby the light intensity is proportional to thatobtained for the control negative and permits the use of the same timingcycles to obtain the same quantity of light for the exposure.

Referring to the drawing an on-oif switch 1 applies power to the system.In order to focus and size the image, room light 2 is switched off byswitch 3, main exposure lamp 4 is turned on by closing switch 5. Themain exposure lamp 4 is preferably a pulsed xenon discharge lamp. Blower6 and enlarger power lift 7 are continuously energized. The on-ofiswitch 1 is supplied from a source of alternating current indicated bypower supply 8.

A timing range for the main exposure can be set between and 330 secondsby the use of series connected timing selector switches 10 and 11.Timing selector switch 10 switches ten resistors 12 and covers the rangefrom 0 to 10 seconds in steps of one second. Timing selector switch 11switches ten resistors 13 and covers the range from zero to 100 secondsin steps of ten seconds. A multiplier switch 16 permits extension ofthese ranges by factors of two or three so that a total time of 330seconds may be had.

A flash panel 17 is controlled to produce a timing range for the flashexposure between 0 and 22 seconds by the use of a twenty-three positionselector switch 14 switching series connected resistors 15. The flashpanel 17 is preferably a luminescent panel, although alternativeconstructions may be used which present a surface uniformly emittinglight.

Separate timing ranges are provided for each separation color, that is,for cyan, magenta, yellow, and black, the timing selector switches forcyan identified as 10, 11, and 14, for magenta 10m, 11m, and 14m, foryellow 10y, 11y and 14y, and for black 10b, 11b and 14b. The timingselector switches are set at the recorded values obtained from the dataof the control negatives.

Light meter probe 20 is positioned in the highlight area of theprojected image on the easel, the light meter is energized by switch 21.Coarse range light meter selector switch 22 and fine range potentiometer23 are set to the recorded values heretofore obtained. The lens apertureof the enlarger is adjusted so that meter 24 produces the same referencereading as heretofore.

The system is now in readiness for the making of the four colorseparation negatives.

Cyan position switch 25 is actuated and through a mechanical interlockfocus switch 5 is opened. Switch 25 is mechanically coupled withswitches 26 and 27 so that all three switches are actuated together.Double pole switch 26 connects timing selector switches 10, 11 and 14 toa common bus 18. Switch 25 has two sets of contacts 25a and 25b. Contact25a completes the circuit of filter wheel motor 28 through normallyclosed contacts 29 of a filter wheel automatic advance relay 30 andcontact 31 of filter wheel commutator switch 32 which causes commutatorswitch 32 to proceed and open at cyan #1 position (switch 31 open).Simultaneously a cyan #1 filter is positioned under the enlarger lens.Closed contact 25b connects coil 34 of relay 30 to open contact 35 ofswitch 36 of timing reset relay 37, and to swinger 40 in normally openposition.

A screen is registered with the film to be exposed and the film isplaced on the easel. The easel is equipped with vacuum channelscontrolled by valves actuated by solenoids 41, each of which arecontrolled by double throw single pole switches 42 which can be thrownto screen or film position. A relay 43 operates contact 44, the selectedsolenoids 41 and vacuum pump 45 when energized through switch 46 closedto one of contacts 47, 48 or 49 respectively providing film, screen andoverlay positions. The film is held in position on the easel by thevacuum. I

Main exposure switch 50 is closed momentarily which energizes capacitorreversal and timing interlock relay 51. Power is applied to the mainexposure lamp 4 through the closed contacts of switch 36.Simultaneously, as will be described later, timing unit 52 is actuated.Relay 51 is self interlocked through its contacts 53. At the expirationof the timed interval as set on selector switches 10 and I l switch 36is momentarily dropped to its contact 35 opening the circuit to the mainexposure lamp 4 and terminating the exposure. While switch 36 is makingmomentary contact with contact 35 relay 34 is energized and interlockedthrough switch 40 until contact 54 of filter wheel commutator switch 32is opened thereby stopping the filter wheel in cyan #2 position.

The screen, already in register, is placed over the film and switch 46is turned to contact 48 (screen) to hold the screen in position. Switch50 is momentarily closed so that the film is exposed for the presetinterval by main exposure lamp 4.

The flash panel is swung into position and switch 55 actuated. Switch 55includes normally closed contact 56 and normally open contact 57.Contact 56 is opened momentarily when switch 55 is actuated to preventpossible misfiring of the timing circuit. Contact 57 is closed to applypower to the coil of flash interlock and control relay 58.

The relay 58 activates normally closed switch 59 which when openeddisconnects capacitors from the timing circuit, also a normally openswitch 60 which is closed to energize and interlock timing relay 51 tostart a flash timed interval. Relay 58 also actuates a double throwswitch 61 having contacts 62. and 63. Normally closed contact 62connects the selector switches 10 and 11 to the timing unit 52 for mainexposure. Contact 63 connects selector switch '14 to the timing unit 52for flash exposure. Relay 58 further activates a double throw switch 64having normally closed contact 65 and normally open contact 66. Closedcontact 65 connects through a normally open switch 68 actuated by therelay '51 to complete a power supply to the main exposure lamp 4.Normally open contact 66 provides an interlock for relay 58 throughswitch 36 and also applies power to the flash panel during the flashexposure cycle.

The timing circuit 52 is described and claimed in my co-pending patentapplication Ser. No. 581,032, filed Sept. 21, 1966, and titled TimingCircuit. The circuit is based on the discharge of capacitors at thestart of a timed interval to a charge of the reverse polarity of amagnitude, when amplified, to trigger controlled rectifier 70 intoconduction, so that relay 3'7 is actuated opening normally closed switch36, and thus deenergizing the interlock circuits of timing relay 51 inthe case of a main exposure, and deenergizing relays 58 and 51 in thecase of a flash exposure.

The timing circuit 52 is supplied by a transformer 71 providing directcurrent by a diode 72 which is filtered by a capacitor 74 and a resistor75. A zener diode 76 regulates the direct current voltage. A voltagedivider 77 provides a voltage of one magnitude to negatively chargecapacitor 79. Additional capacitors 80' and 81 may be switched inparallel with capacitor 79 if desired by switch 16. Transistor 85 isadapted to be turned on by a slight positive potential on its basereceived through diode 86 from capacitor 79. A negative bias is providedfor the control electrode of controlled rectifier 70 by a voltagedivider 87 receiving a controlled negative potential filtered byresistor 89 and capacitor 90 and controlled 'by zener 91. The timingcircuit condition so far described is that present at the start of atiming cycle.

A timing cycle is started by energization of timing relay 51 whichoperates switches 93 and 94 so that the capacitor 79 is dischargedagainst the potential of voltage divider 95 and charged in the reversedirection with a positive going potential. As capacitor 79 becomespositive a diode 86 passes current and transistor '85 is turned on withan amplifying action and a positive potential is produced on the top ofstabilizing capacitor 96 to trigger the gate of controlled rectifier 70.

The operation of the electric system will now be explained in somewhatdifferent language in order to bring out more clearly the novel featuresof the invention.

The electric system includes switching means to connect the exposurelamp 4 to the source of power 8 to provide a timed exposure measured bythe timer 52. The exposure is started by closing starting switch '50which causes to be energized a timing relay '51 controlled by the switch50. Main lamp switching means 6-8 is controlled by the timing relay 51to energize the lamp 4. The timing relay '51 is provided with interlockswitching means 53 and also timer switching means 93 and 94 for startingthe timer 52. It will be remembered that the operation of the timer 52is predicated on the charge of the capacitor 79 to one potential, thecapacitor being reversed in its connection to a somewhat differentpotenti-ona by the switching means 96 and 94 for a charge in the reversedirection, the time interval depending upon the time for the capacitor79 to be charged in the reverse direction. A further control of the timeof charge of the capacitor 79 in the opposite direction is provided bythe resistors of main exposure control means 10 and 11. The timing resetrelay 37 is operable by the timer 52 at the expiration of thepredetermined operating time as determined by main exposure controlmeans :10 and 11. Normally closed switching means 36 controlled by thetiming reset relay 37 is operative to deenergize the timing relay 51 andthereby deenergize the main lamp 4 from the source of power 8.

The next operation requires the flash panel 17 to be actuated for apredetermined length of time from the source of powers. Operation isstarted by actuating the flash panel starting switch 56. Flash panelexposure control means 14 has already been set to determine the time ofoperation of the timer 52. The flash control relay 58 is operated by theflash panel starting switch 56. The flash relay 58 controls double throwswitching means 64 which is normally closed against contact 65 so as toprovide a series circuit for energizing main lamp 4. When the flashrelay 58 is operated to its other position contact 66 energizes theflash relay contact and simultaneously energizes the flash panel 17. Theother double throw switching means 61 of flash relay 58 is normallyclosed to contact 62 connecting the main exposure means 10 and 11 to thetimer 52, but when the flash relay 58 is operated the double throwswitch engages contact 61 in its other position thereby connecting theflash panel exposure control means to the timer 52 for the timedoperation of the flash panel.

While the invention has been described and illustrated with reference tospecific embodiments thereof, it will be understood that otherembodiments may be resorted to without departing from the invention.Therefore the form of the invention set out above should be consideredas illustrative and not as limiting the scope of the following claims.

I claim:

1. An electric system comprising a main exposure lamp, a source ofpower, a timer, a main exposure starting switch, a timing relaycontrolled by the main exposure starting switch, main lamp switchingmeans controlled by said timing relay for energizing said main exposurelamp from said source of power, interlock switching means for saidtiming relay, timer switching means controlled by said timer relay forstarting the timer, main exposure control means for said timeradjustable to set the operating time thereof, a timing reset relayoperable by said timer at the expiration of the operating time thereofas determined by said main exposure control means, normally closedswitching means controlled by said timing reset relay operative todeenergize said timing relay and thereby deenergize said main lamp fromsaid source of power, a flash panel, a flash panel starting switch,flash panel exposure control means for said timer adjustable to set theoperating time thereof, a flash control relay operative by said flashpanel starting switch, a flash relay interlock circuit, double throwswitching means controlled by said flash relay normally in one positionin series with said circuit for energizing said main lamp and in itsother position opening the circuit for energizing said main lamp andenergizing said flash relay interlock circuit and said flash panel, anddouble throw switching means controlled by said flash relay normally inone position connecting said main exposure control means to said timerand in its other position connecting said flash panel exposure controlmeans to said timer.

2. An electric system according to claim 1 in which the main exposurelamp is a pulsed xenon discharge lamp.

3. An electric system according to claim 1 in which the flash panel is aluminescent panel.

4. An electric system according to claim 1 in which the main exposurecontrol means is a plurality of resistors series connected and aselector switch is provided to switch in resistors as desired.

5. An electric system according to claim 1 in which the flash panelexposure means is a plurality of resistors series connected and aselector switch is provided to switch in resistors as desired.

References Cited UNITED STATES PATENTS 2,936,405 5/1960 Waner 315312JOHN w. HUCKERT, Primary Examiner.

J. D. CRAIG, Assistant Examiner.

1. AN ELECTRIC SYSTEM COMPRISING A MAIN EXPOSURE LAMP, A SOURCE OFPOWER, A TIMER, A MAIN EXPOSURE STARTING SWITCH, A TIMING RELAYCONTROLLED BY THE MAIN EXPOSURE STARTING SWITCH, MAIN LAMP SWITCHINGMEANS CONTROLLED BY SAID TIMING RELAY FOR ENERGIZING SAID MAIN EXPOSURELAMP FROM SAID SOURCE OF POWER, INTERLOCK SWITCHING MEANS FOR SAIDTIMING RELAY, TIMER SWITCHING MEANS CONTROLLED BY SAID TIMER RELAY FORSTARTING THE TIMER, MAIN EXPOSURE CONTROL MEANS FOR SAID TIMERADJUSTABLE TO SET THE OPERATING TIME THEREOF, A TIMING RESET RELAYOPERABLE BY SAID TIMER AT THE EXPIRATION OF THE OPERATING TIME THEREOFAS DETERMINED BY SAID MAIN EXPOSURE CONTROL MEANS, NORMALLY CLOSEDSWITCHING MEANS CONTROLLED BY SAID TIMING RESET RELAY OPERATIVE TODEENERGIZE SAID TIMING RELAY AND THEREBY DEENERGIZE SAID MAIN LAMP FROMSAID SOURCE OF POWER, A FLASH PANEL, A FLASH PANEL STARTING SWITCH,FLASH PANEL EXPOSURE CONTROL MEANS FOR SAID TIMER ADJUSTABLE TO SET THEOPERATING TIME THEREOF, A FLASH CONTROL RELAY OPERATIVE BY SAID FLASHPANEL STARTING SWITCH, A FLASH RELAY INTERLOCK CIRCUIT, DOUBLE THROWSWITCHING MEANS CONTROLLED BY SAID FLASH RELAY NORMALLY IN ONE POSITIONIN SERIES WITH SAID CIRCUIT FOR ENERGIZING SAID MAIN LAMP AND IN ITSOTHER POSITION OPENING THE CIRCUIT FOR ENERGIZING SAID MAIN LAMP ANDENERGIZING SAID FLASH RELAY INTERLOCK CIRCUIT AND SAID FLASH PANEL, ANDDOUBLE THROW SWITCHING MEANS CONTROLLED BY SAID FLASH RELAY NORMALLY INONE POSITION CONNECTING SAID MAIN EXPOSURE CONTROL MEANS TO SAID TIMERAND IN ITS OTHER POSITION CONNECTING SAID FLASH PANEL EXPOSURE CONTROLMEANS TO SAID TIMER.